Peter Burrell, Dettori’s business manager, said the jockey had been bitterly disappointed to learn of the fracture after X-rays were taken last night. “He went to Cambridge ­Hospital as a precaution, but he received bad news. The ankle is ­fractured. It is an extremely painful injury. I’m afraid Sunday is out – as is the rest of the season.”

Dettori has quietly and effectively bedded in to his new job as first jockey to Sheikh Joaan bin Hamad Al Thani, one of the new wave of Qatari owners, who has splashed out to buy proven Group One horses.

The jockey’s rehabilitation ­following a six-month ban after ­testing positive for cocaine in Paris in September 2012 was complete when he won the Prix Vermeille on Treve three weeks ago.

Treve has improved physically every day since the Vermeille, according to her trainer Criquette Head-Maarek, and the unbeaten daughter of Motivator is expected to go very close to winning on Sunday.

Dettori’s place on the unbeaten filly will be taken by veteran Thierry Jarnet, who rode her to her first three victories. Jarnet is a star of two decades ago who has revived his career quite remarkably.

He won his first Arc on Subotica in 1992 and his second on Carnegie in 1994. Both were trained by André Fabre, whose main chance on Sunday is 10-1 chance Intello, recent winner of the Prix Prince d’Orange at Longchamp.

In other Arc news, Gerald Mossé was being linked late on Wednesday with Leading Light, the St Leger winner from Ballydoyle, who might have only Ruler Of The World and Ryan Moore from the Aidan O’Brien team for company in the Arc field. The trainer is expected to clarify plans after talking with connections on Wednesday night.

There will be a late addition to the horses entering quarantine for the Melbourne Cup at the weekend.

Voleuse de Coeurs, the brilliant winner of the Irish St Leger for Dermot Weld, has been snapped up for a group of Australian owners, who will send the filly to Mike Moroney.

The deal was struck by the trainer’s brother, Paul.

Voleuse De Coeurs, formerly owned by Lady O’Reilly, is a noted soft-ground horse, so her new owners will be hoping for a change in the weather during the Melbourne spring.

Richard Kingscote has passed up the opportunity to ride at Flemington on Saturday in final preparation for his ride on Michael Owen’s Brown Panther in the cup on Nov 5.

Kingscote had been offered a ride by local trainer Robert Smerdon.

Prominent owner Lloyd Williams has warned that Sea Moon, who he bought out of the Sir Michael Stoute stable, may not be ready for the Australian showcase.

“He might need more time to acclimatise,” said Williams, the leading Australian buyer of European stayers in recent years.

“It was much the same story with Green Moon, who was a bit slow to come to hand in his first season, but then won the cup in his second year.”

Sea Moon is set to run in the Bart Cummings Stakes, which will act as a stepping stone to the cup for many local aspirants.